One result of the side effects of cancer treatments is that patients often can't tolerate or survive a combination of different drugs at the same time—which can limit a doctor's ability to knock out the disease. The head of a Boston-area biotech called Cerulean Pharma thinks the solution is nanoparticle-delivered drugs, which have fewer and less severe side effects. They could make it easier for doctors to mount a multipronged attack on tumors and kill the cells before they can develop a resistance to any one compound.

Cancer cells can develop resistance to individual drugs very quickly, says Oliver Fetzer, CEO of Cerulean. And he points to recent studies showing that different cells within the same tumor can have different genetic mutations. In some cases, that means that a drug that kills cancer cells in one part of a tumor may not work in other parts. This tumor diversity suggests that it would be best to hit cancer cells with multiple drugs at once to make it extremely difficult for the tumor to develop resistance to all therapies.

Nanoparticles could help achieve this goal. The nanoparticles developed by Cerulean are too big to get out of blood vessels and into healthy tissue, but they are the right size to get into tumors because the blood vessels that grow around cancer tissue have pores or gaps that aren't found in healthy tissue.